The invention relates to a device for tensioning at least one tension mechanism of a conveying device. The tension mechanism comprises a multiplicity of feeder aids that extend between a drive wheel and at least one guide wheel. In order to change the tension of the tension mechanism, the wheel center distance between the at least one guide wheel and the drive wheel is adjusted via at least one hydraulic cylinder (which acts directly on the guide wheel). In order to tension the tension mechanism, the hydraulic piston of the hydraulic cylinder (which is displaceably disposed in a pressure chamber), is acted upon by pressure medium from a pressure source via a check valve. The check valve opens toward the pressure chamber.
Conveying devices of the aforementioned type preferably are used in agricultural vehicles to transport conveyed crop (which can be grain, stalk crop, tubers, root vegetables, etc.), via a conveyance path. At least one tension mechanism is provided for this purpose in a form of a chain or belt. Feeder aids are disposed on the chain or belt at a distance from one another. These feeder aids are preferably in the shape of tines, recesses, or plates and convey the particular crop to be transported along a specified conveyance path (which preferably extends between two wheels that guide the tension mechanism).
One of the wheels is designed as a drive element and the other is designed as a guide element. The wheels preferably are formed as drive sprockets or pulleys depending on the design of the tension mechanism. A return region for the tension mechanism and the feeder aids is provided in the region of the conveying device facing away from the transport path. The conveying device preferably is disposed within a housing, wherein two separated chutes by which the conveyed crop is transported (one chute) and by which the conveying elements return (the other chute). Furthermore, such conveying devices include two tension mechanisms, which extend in parallel, and wherein the feeder aids (which are in the form of conveyor slats), are attached to both tension mechanisms.
Optimum functionality of a conveying device having such a design can be achieved by providing the tension mechanism with sufficient tension, i.e. by ensuring that said tension mechanism is not too loose. As a result, inter alia, the feeder aids can be moved in a specified position relative to the crop and the walls of the transport chute. The conveying effect of the conveying device would be greatly limited otherwise if the preload of the tension mechanism decreased. It is therefore necessary to provide means for precisely setting the preload of the tension mechanism. Within this context, devices for tensioning a tension mechanism are known, in which the wheel center distance of the aforementioned wheels is changed manually or automatically.
DE 199 25 691 A1 discloses conveying devices on a self-propelled combine harvester in the form of a grain elevator, a tailings elevator, or a feed rake. Each of these devices for tensioning the tension mechanism comprises at least one single-action hydraulic cylinder, which is supplied with pressurized hydraulic oil from a pressure medium system. A pressure chamber of this single-action hydraulic cylinder is connected to the pressure-medium supply via a check valve in the form of a non-return valve. This ensures that (in the event of diminishing preload on the tension mechanism), pressure medium enters the pressure chamber via the automatically opening non-return valve and displaces the corresponding hydraulic piston in the direction of an increase in the chain tension of the conveying device.
DE 39 15 227 A1 discloses a device for tensioning drive belts provided on the control drive of the internal combustion engine or on the generator drive. An idler pulley is supported on a control arm to act on the slack side of the belt drive. The idler pulley is preloaded by means of a tensioning device comprising a coil spring and a hydraulic cylinder. An external hydraulic system is not required to supply pressure medium to the corresponding hydraulic cylinder since pressure medium is fed to a pressure chamber of the hydraulic cylinder via a non-return valve. The pressure medium originates from an internal accumulator chamber of the hydraulic cylinder that operates as a pressure reservoir.